This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. RF heating will be measured using our 3T MR system and fluoroptic thermometry in human sized swine (60-80 kg). Continuous wave/Pulsed RF will be delivered using a 3T, 7T, 9.4T, or 11.74 T head coil. Temperatures will be measured using a GRE sequence, Shalom's T1r and T2r sequences, and a 3T head coil, and fluoroptic probes. To measure temperatures using MR, temperature calibration will be done using unheated, anesthetized pigs. Anesthesia causes animal to drop their temperatures linearly and uniformly everywhere in the brain. Typically speaking, the core temperature of a 60-80 kg pig drops from 38 to 32 degree C in 10-12 hours. Temperatures in the animal brain will be measured using fluoroptic probes for this duration. PRF/T1r/T2r will be measured over the duration and their slope maps will be correlated to the linearly decreasing fluoroptic temperatures. The developed slope maps will be used to estimate temperatures in RF heated pigs. Permission will be sought from the Siemens before any RF heating work will be commenced on the 3T.